What a great collection of advice!
I was lucky to have a music teacher at school who gave proper voice training to choir members. It is only now, 30+ years later that I realise what a valuable foundation that was, and all for free!

My OH started with singing lessons about 2 years ago at the age of 43. His first teacher was great at the technical aspects (breath, vocal production) but was rather tied into musical stage show type singing and also did not really work with the psychological aspects of singing. He then swapped teachers and finds his current teacher is both versatile and responsive - he is finding his own unique voice, is safely developing his vocal range, and picking up the techniques too whilst overcoming some personal barriers about performing. In turn he has felt able to sing in front of others (initially at singalong sessions where he could opt in or out of choruses discreetly).

Now we are singing together with a friend as an oly timey trio and have done a few gigs since autumn. So you never know where your NY resolution may lead, especially if you are already an instrument player.

There has been lots of fantastic suggestions given and I can only emphasise the need to start with good relaxation, diaphragm breathing and vocal warm ups and to aim for speech-level singing, in order to avoid the sense of strain that you described in your first post.

Good luck and have fun finding your voice!