#2. Brock Lesnar vs. Finn Balor
This isn't necessarily a fresh feud for Brock Lesnar, but it could be an interesting direction to go in - especially if WWE wants to re-establish Finn Balor as a top face on SmackDown. Brock Lesnar and first ever Universal champ crossed paths at the Royal Rumble 2019 pay-per-view, where Lesnar won.
It wasn't a conventional squash match, and Finn Balor certainly didn't look bad. However, it would be a good feud, especially since Balor had a title shot taken away from him on SmackDown.
#1. Brock Lesnar vs. Drew McIntyre
This would be a logical direction. Brock Lesnar doesn't always have to be involved in title feuds, but since WrestleMania 33, that's all he has been a part of. Drew McIntyre was the last man he faced at WrestleMania 36 in 2020, and it would make sense for him to renew that rivalry.
After convincingly putting away Jinder Mahal, Drew McIntyre is looking to build himself back up as a WWE title contender. A non-title feud with Brock Lesnar would be a good step to build Drew McIntyre. It could also perhaps be more refreshing than another rematch with Roman Reigns.