I used both radicale and baikal. Both work great. Both support CalDAV and CardDAV, to sync with them you need thr davx5 app on android. I ended up going with radicale because it supports proxy authentication and I can use it with Authelia

Second this. Works really well in a stable distro like Proxmox. Unfortunately however the community is only on discord. With some other patches linked there you can also use the gpu both on the host and split in vGPUs for virtual machines at the same time. I used it for some time on Arch Linux host + Win10 VM for CAD. Worked fine, but frequent arch updates borked everything often. On proxmox I never had such problems.

You know what, I like it more than LinkGuardian. Great suggestion!

For however needs it, LinkGuardian on Android (izzyondroid for fdroid) offers the same thing!