I have about 30 numbers I use personally through voip.ms. They are all SMS/MMS enabled without TCR issues, signups, or requirements. Heck, I just checked and couldn't even find a way to register for TCR. Read into that how you'd like. I've had no issues with messages not being delivered to any mobile providers, but I honestly haven't tested this thoroughly. I just haven't had any messages I've sent not go through.

They have SIP support as well as an online SMS/MMS portal you can access from desktop or mobile. The only issue is they are still working on support to receive MMS by SIP protocol which might eliminate them from your consideration. You can send MMS by SIP currently though.

Phone number is only $0.85/month and then pay-per-usage of $0.0075/SMS and $0.02/MMS. Probably cheap enough to purchase a number to test it out to see if it will meet your needs. I've used them for years, have had no issues, and am happy with their service.

The only knock on using voip.ms is the initial setup is a little tedious and you need to understand the basics of how they are working with each part of the VOIP protocol. Their FAQs and guides are pretty well written to help you get set up.

I start with voip.ms and see if they meet my needs due to great customer service as well as low price and high stability. Then I look elsewhere if I need something voip.ms doesn't support.

edit: spacing for readability