To listen to LPs in surround, it appears there is no phono turntable input on your A-V receiver, common issue.
Easily solved with an inexpensive phono preamp and cable.
CDs, too, are often more immersive in Dolby PL Music or Neo Music mode.
Right now I'm listening to 1970 Jethro Tull Benefit on DVD in 5.1 DTS 96/24.
Have you explored the Polls section of the forum?
Great place to see what's been released in quad and surround and read reviews and banter.
https://www.quadraphonicquad.com/TabbedPollChart.htm
Other 1970-era recent Quad re-issues I've listened to this week:
- The Doors - The Singles bonus blu-ray Best of The Doors 1973 Quad Mix ($18, 2 CD - 1 BDA) https://www.amazon.com/gp/product/B07377SQTZ
- Chicago, first nine albums vintage quad mix blu-ray
- Allman Brothers - Complete Fillmore East (six hours of audio) & Idlewild South 5.1 blu-ray
- Jethro Tull - Stand Up, Aqualung DVD
- In The Court of the Crimson King 5.1 DVD
- Supersession 5.1 SACD (new, on sale for $10)
- Elton John - Tumbleweed Connection SACD