LoL, we dont. Accounts are issued to individuals. My local sysadmin cosplay group encourages people to make their own instances with small user counts and to federate the services with each other. That way if one users network goes out as residential networks are want to do, communication is not completely down for the collective.

Mine's only for people I know personally, so it's backed by my LDAP server and registration is disabled in Synapse. I use my regular onboarding process to create the new LDAP user and grant access to Synapse.

I don’t allow registration but I can manually create accounts. My server is just for me and a few others so this is perfectly fine for me

Does Synapse have an option to create a one-time registration token with short expiry? I'd do that if my community is small enough.

For friends that I know, they can just ask me and I'll give them a login secret. I don't have the headspace to manage fedidrama.

We allow registration with a one time token only and a hidden registration page. The token is generated via bot by an admin/mod.

Open registration if and only if you are ready for routine maintenance, creating cleaning schedules, applying spam filters, balancing resource usage, etc. Not to discourage, but for you to know what you really want. If server is for friends and family, just leave registration closed.

My recommendation, as someone hosting a public server is to first host the server for yourself, play for some time, join some rooms on other servers, then invite friends, then if you feel ready and willing open it to the public.

Matrix Authentication Service is good to have, as you can use next-gen Element X which is most polished app as for now.

I recently migrated my Synapse to MAS.
The next night, I dreamed that my sleep is now modern, extensible, secure, and uses XML.

Use Continuwuity instead of synapse... Faster and much less resource hungry