I haven't used it much if at all in the past year, but I finally took the last step and deleted it!
Sorry if this is low effort I just don't have anyone I know to share it with.
It is all free to use, but you will likely have some expenses with the self-hosting. If you do it yourself at home, you require hardware and power to run it on, and you would be well off having some additional backup solution off-site as well that would add to the cost. If you host on a VPS (like I do), you have the running costs of renting that server space.
I self host with Baikal. On android, you need Davx5 (on fdroid) to tie it into the OS but on your desktop (windows and Linux at least) calDAV will just be an option. Baikal supports CardDAV for contacts as well if you're into that.