6th year medical waivers (redshirts) are not unusual, (Will Egolf & Sam Singh both got one), so I think there's no doubt he will qualify and stay at Nebraska for his final year. Especially in Rienk's case where 2020-21 doesn't count against his eligibility, and thus, he's really only used 3 years of athletic eligibility- 2021-22, 2022-23, and 2023-24.
I think everyone associated with Bradley would love to have him back, but I think that's a longshot.
Also - back to the original topic - bordering on irrelevant now but Missouri State's best player Dez White, averaging 14 ppg & 37% from 3-pt, is in the portal