I'm on the Join my Band and Bandmix mix. Had success with both.
Also looked at local Facebook groups. There's generally one or two groups in your area. I just searched FB for musicians wanted in my area.
Once you get a foot in the door and you're reliable and friendly enough you will find offers coming in from bands you meet looking for a bass player. I'm 65 and up until recently was in 3 completely different band styles. Glam Rock, punk rock and classic rock but was all a bit much and cut it back to the Glam band which is more successful.
Don't be afraid to take on a band that's not what you listen to. It's a foot in the door
All the very best with it.
Dave