Hi all,
Freshly built BigBlueButton 2.3.12, on Ubuntu 18.04, inside an LXC (I've successfully ran BBB within CTs/LXCs for years with no dramas, on my own metal servers). bbb-conf --version below.
Transferred recordings across by rsyncing /var/bigbluebutton/published/, /var/bigbluebutton/unpublished/, and /var/bigbluebutton/recording/raw/ and fixed up permissions.
I had to make some extra adjustments for html5 and freeswitch to work due to new scheduling issues under LXC (haven't on previous versions). Previous recordings are all playing perfectly.
Just noticed that recordings over the last 3 days are not playing. I'm getting 404, with console showing 404 for the webcam.

I have requested the recordings to be re-processed. They complete without error. The video is showing in the raw folder. Process log showing below.
# bbb-conf --check
bbb-conf --check
BigBlueButton Server 2.3.12 (2427)
Kernel version: 5.11.22-3-pve
Distribution: Ubuntu 18.04.5 LTS (64-bit)
Memory: 8388 MB
CPU cores: 12
/etc/bigbluebutton/bbb-web.properties (override for bbb-web)
/usr/share/bbb-web/WEB-INF/classes/bigbluebutton.properties (bbb-web)
defaultGuestPolicy: ALWAYS_ACCEPT
svgImagesRequired: true
/etc/nginx/sites-available/bigbluebutton (nginx)
server_name: ihr3.*****.com
port: 80, [::]:80
port: 443 ssl
/opt/freeswitch/etc/freeswitch/vars.xml (FreeSWITCH)
local_ip_v4: 192.99.***.**
external_rtp_ip: 192.99.***.**
external_sip_ip: 192.99.***.**
/opt/freeswitch/etc/freeswitch/sip_profiles/external.xml (FreeSWITCH)
ext-rtp-ip: $${local_ip_v4}
ext-sip-ip: $${local_ip_v4}
ws-binding: 192.99.***.**:5066
wss-binding: 192.99.***.**:7443
/usr/local/bigbluebutton/core/scripts/bigbluebutton.yml (record and playback)
playback_host: ihr3.*****.com
playback_protocol: https
ffmpeg: 4.2.4-1ubuntu0.1bbb2~18.04
/etc/bigbluebutton/nginx/sip.nginx (sip.nginx)
proxy_pass: 192.99.***.**
protocol: http
/usr/local/bigbluebutton/bbb-webrtc-sfu/config/default.yml (Kurento SFU)
kurento.ip: 192.99.***.**
kurento.sip_ip: 192.99.***.**
localIpAddress: 192.99.***.**
recordScreenSharing: true
recordWebcams: true
codec_video_main: VP8
codec_video_content: VP8
/usr/share/meteor/bundle/programs/server/assets/app/config/settings.yml (HTML5 client)
build: 1833
kurentoUrl: wss://ihr3.*****.com/bbb-webrtc-sfu
enableListenOnly: true
sipjsHackViaWs: true
/usr/share/bbb-web/WEB-INF/classes/spring/turn-stun-servers.xml (STUN Server)
# cat /var/log/bigbluebutton/presentation/process-23497777a69cd23f27d633b8af6b4aa626c7d22d-1629661524835.log
# bbb-conf --version
BigBlueButton Server 2.3.12 (2427)
ii bbb-apps-akka 2.3.0-100 all BigBlueButton Apps (Akka)
ii bbb-config 1:2.3.0-91 amd64 BigBlueButton configuration utilities
ii bbb-etherpad 1:2.3.0-51 amd64 The EtherPad Lite components for BigBlueButton
ii bbb-freeswitch-core 2:2.3.0-24 amd64 BigBlueButton build of FreeSWITCH
ii bbb-freeswitch-sounds 1:1.6.7-3 amd64 FreeSWITCH Sounds
ii bbb-fsesl-akka 2.3.0-55 all BigBlueButton FS-ESL (Akka)
ii bbb-html5 1:2.3.0-1833 amd64 The HTML5 components for BigBlueButton
ii bbb-libreoffice-docker 1:2.3.0-55 amd64 BigBlueButton setup for LibreOffice running in docker
ii bbb-mkclean 1:0.8.7-4 amd64 Clean and optimize Matroska and WebM files
ii bbb-playback 1:2.3.0-18 amd64 BigBlueButton playback
ii bbb-playback-presentation 1:2.3.0-13 amd64 BigBluebutton playback of presentation
ii bbb-record-core 1:2.3.0-36 amd64 BigBlueButton record and playback
ii bbb-web 1:2.3.0-92 amd64 BigBlueButton API
ii bbb-webrtc-sfu 1:2.3.0-34 amd64 BigBlueButton WebRTC SFU
ii bigbluebutton 1:2.3.0-7 amd64 Open source web conferencing platform (bbb)
ii ffmpeg 7:4.2.4-1ubuntu0.1bbb2~18.04 amd64 Tools for transcoding, streaming and playing of multimedia files
ii libavcodec58:amd64 7:4.2.4-1ubuntu0.1bbb2~18.04 amd64 FFmpeg library with de/encoders for audio/video codecs - runtime files
ii libavdevice58:amd64 7:4.2.4-1ubuntu0.1bbb2~18.04 amd64 FFmpeg library for handling input and output devices - runtime files
ii libavfilter7:amd64 7:4.2.4-1ubuntu0.1bbb2~18.04 amd64 FFmpeg library containing media filters - runtime files
ii libavformat58:amd64 7:4.2.4-1ubuntu0.1bbb2~18.04 amd64 FFmpeg library with (de)muxers for multimedia containers - runtime files
ii libavresample4:amd64 7:4.2.4-1ubuntu0.1bbb2~18.04 amd64 FFmpeg compatibility library for resampling - runtime files
ii libavutil56:amd64 7:4.2.4-1ubuntu0.1bbb2~18.04 amd64 FFmpeg library with functions for simplifying programming - runtime files
ii libopusenc0 0.2.1-1bbb1 amd64 High-level API for encoding Ogg Opus audio streams
ii libpostproc55:amd64 7:4.2.4-1ubuntu0.1bbb2~18.04 amd64 FFmpeg library for post processing - runtime files
ii libswresample3:amd64 7:4.2.4-1ubuntu0.1bbb2~18.04 amd64 FFmpeg library for audio resampling, rematrixing etc. - runtime files
ii libswscale5:amd64 7:4.2.4-1ubuntu0.1bbb2~18.04 amd64 FFmpeg library for image scaling and various conversions - runtime files