A password manager can be considered critical infrastructure; beyond privacy and uptime/access considerations, you should also consider what happens if you lose all of your data - Do you have backups? Are the backups 3-2-1 redundant? Do you have a ready-to-go docker compose to get yourself up and running locally in a pinch?

I self-hosted bitwarden (vaultwarden) for several years and it became evident to me that it was important enough to use the hosted service - especially as I was already paying Bitwarden to support their open source business.

If your issue is with the authenticator, then why not just switch authenticators? I've been quite happy with Authy over the years.

Sure, self hosting can be more secure, but if it's not on your own hardware, I don't see how moving to render is better. You're still using a third party to host your most sensitive information.

Have you considered using Bitwarden Premium? It has TOTP support and is $10/year currently.

Also, regardless of how your hosting your data, it's probably good to keep a secured backup of your vault or two just in case something unexpected happens.

there’s also Aegis and 2FAS, but I have no idea about WebDAV servers and also don’t want to rely on Google Drive for backup, also because I’m moving away from Google services.

If your only issue are the backups, then you can still use aegis with automatic encrypted backup to a folder in your device and then use syncthing to automatically send it to your machine. From there use any other backup solution like duplicati or restic.
(Remember that syncthing is not a backup solution, it should only be used as a way to automatically sync files between devices) (People have had many issues with duplicate, but I've only seen posts about huge amounts of data, for something like aegis backups has been working fine for me)

I'd also recommend you asking in !selfhosted@lemmy.world

What would happen if Render changes their plans and I lose access to the database? Will I still have access to the last-stored cache on my browser extension and mobile phone?

Yes, the bitwarden client will simply treat it as being offline. You should check the docs on how to migrate to a new server so you can be prepared.

And since I’m running a Rust infrastructure, would it use less of the free plan bandwidth that Render assigns?

No. ~~Bandwidth is up to the network stack to determine, not the programming language. Generally, your app and OS will use as much as avalable unless otherwise throttled.~~

I just looked it up, and their "bandwidth" is not a measure of bandwidth, but a data quota. The answer is still "no" because it's about how much data is transferred in total, which has also little to do with the language in this case. Despite the difference of some negligible amount of bytes of overhead, vaultwarden's limited by the format the database is in. To lower data usage, try reducing how often you automatically sync the clients with your server.

I'm planning to run Vaultwarden on a free instance of render.com, and I wanted to know if this was a good idea? Has anyone over here tried this?

I have not tried this, but i am opinionated: on one hand, self-hosting will always be your most reliable and private option. However, if you have judged other pursuits a more valuable use of your time and mental energy, then it's probably worth the $20/month (or whatever) if and when your server lands in reorganization jail.

The biggest issue would be your privacy, which almost always goes out the door when money comes into the picture.

I'd pay the $10/yr premium if you can swing it. The emergency contact recovery feature alone was more than worth it to me.

For 2FA, I highly recommend Aegis. I switched from both Google and Microsoft authenticator apps earlier this year and it's been great. I have the backups running automatically and it dumps it into a folder the Seafile is syncing for me. So not only do I have the backups on the server, but on the clients as well. Seafile is then backed up to an encrypted B2 bucket for further redundancy.

I can't answer most of these except that as long as the render-affixed URL supports https you should have no issues and if it does die you ahould have the last synced cache in your browser. Been able to use my vaultwarden extensions offline no problem.

As far as I know, you'll have a last syched copy in your cache. Test it with no internet con! Try to export your data without internet.

I'm using vaultwarden for like 4 year now, but on my personal server at home. Btw a raspberry pi is enough to run vaultwarden.

You could take a look at reverse proxys and dyndns services (like duckdns -> free). I started like this. Now I have my own domain, but that is not mandatory!

I don't know about render.com, but as long you have a HTTPS domain, you can just use any domain.
Also, I think many services will notify you about changes of their pricing, so you can just back up the server and move them somewhere before something going up.
Some good info about Vaultwarden is in the wiki, including some installation source, there are docker, binaries, and rust, so you can pick one of them.

KeePass + Syncthing works also for OTPs (you can even use OTP without a phone).