1Password 7.9.10 Safari extension not working (Mojave)

1Password prompted me to upgrade from 7.9.9 to 7.9.10, stating that due to changes in Chromium, the browser extension would soon stop working in those browsers, but that if one was on an older machine and OS, one could continue to use the 1Password browser extension for Safari.
I am running Safari 14.1.2 under MacOS 10.14.6 Mojave, and after upgrading to 1Password 7.9.10, the Safari browser extension stopped working. First, I received incessant warning pop-ups that "SafariPluginUpdateNotifier quit unexpectedly". I then "Quit 1Password Completely", quit Safari, and rebooted. Now, the SafariPluginUpdateNotifier warning is gone, but the 1Password extension in Safari is gone as well, and I cannot redownload it from Apple’s AppStore since the version there requires at least MacOS 10.15. Running "Install Browser Extensions…" from within 1Password 7 does not help; it neither produces an error message nor does it lead to the extension showing up in Safari.

What can I do to remedy this?

Below are the last lines from my Console log for 1Password (I tried to attach the whole log since last reboot, but neither .txt. nor .zip file format was accepted):

default 13:15:02.998881 +0200 1Password 7 [C7 Hostname#cd7fd611:443 tcp, url hash: 93166f76, tls] cancel
default 13:15:02.999019 +0200 1Password 7 [C7 Hostname#cd7fd611:443 tcp, url hash: 93166f76, tls] cancelled
[C7.1 192.168.0.130:52395<->IPv4#df994602:443]
Connected Path: satisfied (Path is satisfied), interface: en0, ipv4, dns
Duration: 180.606s, DNS @0.000s took 0.017s, TCP @0.020s took 0.025s, TLS took 0.029s
bytes in/out: 18842/1289, packets in/out: 20/9, rtt: 0.030s, retransmitted packets: 0, out-of-order packets: 0
default 13:15:02.999056 +0200 1Password 7 0.000s [C7 Hostname#cd7fd611:443 resolver] path:start
default 13:15:02.999078 +0200 1Password 7 0.000s [C7 Hostname#cd7fd611:443 resolver] path:satisfied
default 13:15:02.999098 +0200 1Password 7 0.000s [C7 Hostname#cd7fd611:443 resolver] resolver:start_dns
default 13:15:02.999117 +0200 1Password 7 0.017s [C7 Hostname#cd7fd611:443 resolver] resolver:receive_dns
default 13:15:02.999142 +0200 1Password 7 0.018s [C7.1 192.168.0.130:52395<->IPv4#df994602:443 socket-flow] path:start
default 13:15:02.999233 +0200 1Password 7 0.018s [C7.1 192.168.0.130:52395<->IPv4#df994602:443 socket-flow] path:satisfied
default 13:15:02.999265 +0200 1Password 7 0.020s [C7.1 192.168.0.130:52395<->IPv4#df994602:443 socket-flow] flow:start_connect
default 13:15:02.999362 +0200 1Password 7 0.045s [C7.1 192.168.0.130:52395<->IPv4#df994602:443 socket-flow] flow:finish_transport
default 13:15:02.999404 +0200 1Password 7 0.045s [C7 Hostname#cd7fd611:443 resolver] flow:finish_transport
default 13:15:02.999433 +0200 1Password 7 0.074s [C7.1 192.168.0.130:52395<->IPv4#df994602:443 socket-flow] flow:finish_connect
default 13:15:03.999530 +0200 1Password 7 0.074s [C7 Hostname#cd7fd611:443 resolver] flow:finish_connect
default 13:15:03.999569 +0200 1Password 7 0.074s [C7.1 192.168.0.130:52395<->IPv4#df994602:443 socket-flow] flow:changed_viability
default 13:15:03.999593 +0200 1Password 7 0.074s [C7 Hostname#cd7fd611:443 resolver] flow:changed_viability
default 13:15:03.999831 +0200 1Password 7 180.606s [C7] path:cancel
default 13:15:03.000746 +0200 1Password 7 nw_endpoint_flow_protocol_disconnected [C7.1 IPv4#df994602:443 cancelled socket-flow (null)] Output protocol disconnected
default 13:15:03.000889 +0200 1Password 7 nw_connection_report_state_with_handler_locked [C7] reporting state cancelled
default 13:15:03.000958 +0200 1Password 7 TIC TCP Conn Destroyed [7:0x60000396ef40]
error 13:15:03.001149 +0200 1Password 7 nw_protocol_boringssl_get_output_frames(1301) [0x7fe7b7708c30] get output frames failed, state 8196
error 13:15:03.001233 +0200 1Password 7 nw_protocol_boringssl_get_output_frames(1301) [0x7fe7b7708c30] get output frames failed, state 8196
default 13:15:03.001933 +0200 1Password 7 success removing entry for host config 0x600000ae75a0
error 13:15:03.002017 +0200 1Password 7 TIC Read Status [7:0x0]: 1:57
error 13:15:03.002047 +0200 1Password 7 TIC Read Status [7:0x0]: 1:57
error 13:15:03.002089 +0200 1Password 7 TIC Read Status [7:0x0]: 1:57
error 13:15:03.002152 +0200 1Password 7 TIC Read Status [7:0x0]: 1:57
default 13:16:26.169219 +0200 pkd plugin /Applications/1Password 7.app/Contents/PlugIns/1PasswordSafariAppExtension.appex is still valid.
default 13:18:58.303569 +0200 1Password 7 27366555: RECEIVED OUT-OF-SEQUENCE NOTIFICATION: 237 vs 676, 513,
default 13:20:06.942719 +0200 pkd plugin /Applications/1Password 7.app/Contents/PlugIns/1PasswordSafariAppExtension.appex is still valid.
default 13:20:55.552571 +0200 1Password 7 27366555: RECEIVED OUT-OF-SEQUENCE NOTIFICATION: 241 vs 692, 513,
default 13:21:14.808391 +0200 1Password 7 27366555: RECEIVED OUT-OF-SEQUENCE NOTIFICATION: 243 vs 694, 513,
default 13:21:24.918977 +0200 1Password 7 27366555: RECEIVED OUT-OF-SEQUENCE NOTIFICATION: 245 vs 696, 513,
default 13:21:34.494628 +0200 1Password 7 27366555: RECEIVED OUT-OF-SEQUENCE NOTIFICATION: 247 vs 698, 513,
default 13:22:44.785575 +0200 1Password 7 27366555: RECEIVED OUT-OF-SEQUENCE NOTIFICATION: 252 vs 708, 513,

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1Password Version: 7.9.10
Extension Version: Not Provided
OS Version: macOS 10.14.6
Browser:_ Safari 14.1.2
Referrer: forum-search:https://1password.community/search?Search=1Password%207.9.10%20Safari%20extension%20not%20working%20(Mojave)