How do I check if they are online?
Discussion
You can check it by using node management tools like RTL (Ride the lightning), Thunderhub, LNDg, etc. In which environment are you running your lightning node? Is it LND or CLN or eclair? Are you using umbrel OS?
Is the channel open or inactive? That will tell you whether the peer is up or down.
RTL reports...
State
Channeld Normal
Connected
No
Disconnected
I don't have this exact wording in my rtl.. And the format you posted is funky but the channel seems inactive.
In my RTL I have green dot for active channels and grey dot for inactive channels.
To be honest not much you can do if the remote peer is offline. Try contacting them... At some point you may have to force close the channel.
Force close is a standard part of lightning. Just more expensive and slower than normal (cooperative) close.