Kylo we're using PHP 8.x for all forums:
Flarum core 1.2.1
PHP version: 8.0.14
MySQL version: 5.5.5-10.6.5-MariaDB-1:10.6.5+maria~focal
Loaded extensions: Core, date, libxml, openssl, pcre, zlib, filter, hash, json, pcntl, Reflection, SPL, session, standard, sodium, mysqlnd, PDO, xml, calendar, ctype, curl, dom, mbstring, FFI, fileinfo, ftp, gd, gettext, gmp, iconv, intl, exif, mysqli, pdo_mysql, Phar, posix, readline, shmop, SimpleXML, sockets, sysvmsg, sysvsem, sysvshm, tokenizer, xmlreader, xmlwriter, xsl, Zend OPcache
+-------------------------------------+-------------+--------+
| Flarum Extensions | | |
+-------------------------------------+-------------+--------+
| ID | Version | Commit |
+-------------------------------------+-------------+--------+
| flarum-flags | v1.2.0 | |
| flarum-sticky | v1.2.0 | |
| flarum-likes | v1.2.0 | |
| fof-formatting | 1.0.2 | |
| flarum-tags | v1.2.0 | |
| flarum-suspend | v1.2.0 | |
| flarum-nicknames | v1.2.0 | |
| flarum-lock | v1.2.0 | |
| flarum-approval | v1.2.0 | |
| afrux-forum-widgets-core | v0.1.7 | |
| flarum-markdown | v1.2.0 | |
| zerosonesfun-member | 1.2 | |
| v17development-seo | v1.8.0 | |
| the-turk-stickiest | 2.0.3 | |
| the-turk-mathren | 1.0.3 | |
| sycho-profile-cover | v1.3.1 | |
| sycho-advanced-extension-categories | v0.1.3 | |
| nearata-twofactor | v2.0.1 | |
| nearata-no-self-likes | v1.2.0 | |
| migratetoflarum-canonical | 1.0.0 | |
| mickmelon-coloured-usernames | 0.1.1 | |
| michaelbelgium-discussion-views | v7.1.2 | |
| malago-fancybox | 0.3.0 | |
| kilowhat-audit-free | 1.5.1 | |
| justoverclock-hot-discussions | 0.1.2 | |
| jslirola-login2seeplus | v0.2 | |
| ianm-synopsis | 1.2.0 | |
| ianm-level-ranks | 1.0.0 | |
| ianm-html-head | 1.1.0 | |
| fof-user-directory | 1.2.2 | |
| fof-user-bio | 1.0.2 | |
| fof-upload | 1.1.0 | |
| fof-terms | 1.1.2 | |
| fof-split | 1.0.1 | |
| fof-socialprofile | 1.1.1 | |
| fof-sitemap | 1.0.3 | |
| fof-secure-https | 1.0.1 | |
| fof-reactions | 1.0.4 | |
| fof-profile-image-crop | 1.0.1 | |
| fof-prevent-necrobumping | 1.0.1 | |
| fof-pretty-mail | 1.0.1 | |
| fof-polls | 1.0.5 | |
| fof-nightmode | 1.2.1 | |
| fof-masquerade | 2.1.0 | |
| fof-links | 1.0.3 | |
| fof-ignore-users | 1.0.2 | |
| fof-filter | 1.0.2 | |
| fof-drafts | 1.0.3 | |
| fof-disposable-emails | 1.0.0 | |
| fof-discussion-thumbnail | 1.0.1 | |
| fof-default-user-preferences | 1.0.0 | |
| fof-best-answer | 1.1.9 | |
| fof-ban-ips | 1.0.2 | |
| fof-analytics | 1.0.0 | |
| flarum-subscriptions | v1.2.0 | |
| flarum-statistics | v1.2.0 | |
| flarum-mentions | v1.2.0 | |
| flarum-lang-english | v1.2.0 | |
| flarum-lang-chinese-simplified | v1.1.1.1220 | |
| ffans-clipboardjs | v1.0.0 | |
| datlechin-signup-button | v0.1.0 | |
| clarkwinkelmann-group-list | 1.0.0 | |
| clarkwinkelmann-first-post-approval | 1.0.0 | |
| clarkwinkelmann-emojionearea | 1.0.0 | |
| clarkwinkelmann-create-user-modal | 1.3.0 | |
| clarkwinkelmann-bookmarks | 1.0.0 | |
| askvortsov-rich-text | v2.1.6 | |
| askvortsov-pwa | v3.1.2 | |
| askvortsov-moderator-warnings | v0.6.1 | |
| askvortsov-markdown-tables | v1.2.1 | |
| askvortsov-discussion-templates | v0.8.3 | |
| antoinefr-money | v1.2.0 | |
| afrux-news-widget | v0.1.1 | |
| afrux-forum-stats-widget | v0.1.1 | |
| acpl-mobile-tab | 1.1.0 | |
+-------------------------------------+-------------+--------+
Base URL: https://www.luocun.org
Queue driver: sync
Mail driver: smtp
Debug mode: off
I rather think that we're way too up to date with our extensions and composer packages, if you know what I mean. Perhaps one of them introduced a breaking change which made your extension not function properly
