Options:

• Just start it from the terminal with torsocks
• Use application-specific proxy settings
• Since torsocks simply uses LD_PRELOAD, you could try to make this apply globally by adding the torsocks library to ld.so.preload. Just put the path returned by torsocks show in /etc/ld.so.preload.

Either use the --proxy option of yt-dlp, or use torsocks to transparently torify any application.

Here is a config template to run an obfs4 bridge, make changes as required:

BridgeRelay 1

# Replace "TODO1" with a Tor port of your choice.
# This port must be externally reachable.
# Avoid port 9001 because it's commonly associated with Tor and censors may be scanning the Internet for this port.
ORPort TODO1

ServerTransportPlugin obfs4 exec /usr/bin/obfs4proxy

# Replace "TODO2" with an obfs4 port of your choice.
# This port must be externally reachable and must be different from the one specified for ORPort.
# Avoid port 9001 because it's commonly associated with Tor and censors may be scanning the Internet for this port.
ServerTransportListenAddr obfs4 0.0.0.0:TODO2

# Local communication port between Tor and obfs4.  Always set this to "auto".
# "Ext" means "extended", not "external".  Don't try to set a specific port number, nor listen on 0.0.0.0.
ExtORPort auto

# Replace "" with your email address so we can contact you if there are problems with your bridge.
# This is optional but encouraged.
ContactInfo 

# Pick a nickname that you like for your bridge.  This is optional.
Nickname PickANickname

You can also use the reachability test to check if everything is configured correctly. If it is reachable and bootstrapping reaches 100% you should be set.

Set SocksPort if you want to connect your browser (don’t confuse this with ORPort). Default is localhost:9050.

I’m not on NixOS, but I have a decent working knowledge of Tor.

Not quite clear on what you’re trying to do, are you trying to run a relay, or just connecting to the Tor network and pointing your browser to the socks proxy?

Arti (the official Tor implementation in Rust) is not a complete replacement for the Tor C implementation yet. Hidden service support is disabled by default (due to the lack of a security feature that could allow guard discovery attacks), and bridges don’t work either. If you don’t understand Tor very well stick with the old router.