>>2617885t.beginner mountaineer
you shouldn't travel on a glacier or class 5 terrain alone but for the bigger peaks you can usually find randos asking for partners on Alltrails and then just email or dm them and climb with them and make friends that way. If you go to a local climbing gym the people you belay with could be your next mountaineering partners. I have a couple of friends who are a mix of the stuff and my dad but the hardest part really is the scheduling. Also, for a lot of mountains in PNW, you can do them solo if you are comfortable and take the usually easiest routes at certain times of year
Adams: south face (June)
Hood: Hogsback (June to Early July)
Shasta: Clear Creek (may to September)
Saint Helens: Ptarmigan (basically any time of year other than early winter)
All four of these are fabulous peaks without major glaciers on these routes (Adams and hood technically have them but the crevasses are a nonissue on these routes) and a great way to start. For something like Rainier, Baker, Jefferson, North Sister, you are gonna want a glacier team who knows that they are doing or buddies who can belay you. You can also do a guided course (go for a course, not a guided climb, because you spend more time with peeps, get skills) and learn those skills and meet like-minded people there.
If I don't have anyone to go with to climb Ill usually just do super long day hikes or peakbag class 4s and below. Good for your fitness (walking up stairs is the most relevant mountaineering fitness) and you learn as much about planning and weather and what you can really do.
