After not shooting any B&W for 40-plus years, I just started shooting mono in my old Pentax MX(s) again. I have collected a small list of labs recommended by members of another forum. I haven't tried any of these yet, but I trust the folks who say these labs are good:
The Darkroom, San Clemente, CA,
The Darkroom | 35mm Film Developing by Mail
Richard Photo Lab, Los Angeles,
Richard Photo Lab
Photolab (Photolaboratory), Berkeley, CA
High Quality Film processing at Photolab
Precision Photo, Austin, TX
B&W Film Processing- 35mm
For my first few rolls of b&w I have been trying out something different - there is a lab in Stuart, Iowa called DR5 that can develop many standard b&w films (but not all) as positives. That is, b&w "chromes" or slides. If you plan to scan the film rather than making prints in a chemical darkroom, DR5 claims their reversal process has several advantages compared to the same films developed as negatives (finer grain, wider dynamic range, higher D-max, etc). You probably don't want to fall in love with b&w positives if you plan on home developing because I doubt dr5's propritary process can be duplicated at home. And there are very few other options for b&w positives in the US.
Be warned, DR5's website is Not Pretty. In fact, it's almost laughably bad. But if you want to check it out, this page is as good a place to start as any
dr5CHROME THE ONLY UNIVERSAL b&W SLIDE PROCESSING - For most ALL film-types. The Highest Quality SCALA PROCESSING - WORLDWIDE
... and these two pages show some comparisons to conventional processing
dr5 CHROME - Black and White transparency process + THE ONLY RELIABLE SCALA PROCESSING WORLDWIDE dr5 CHROME - Black and White transparency process + THE ONLY RELIABLE SCALA PROCESSING WORLDWIDE
I have no affiliation; not even really recommending them because my experiece is still very limited. Anyway, like I said, it's something different.
Ilford HP5 Plus developed as positives by dr5 and home scanned on my old Minolta film scanner; post processed in Photoshop: