A lot of people are inputting 1099R and backdoors already it's likely working fine so I wouldn't jump to conclusion it's a TT issue - it's something to troubleshoot here if you provide more info or screenshots it might help. I do agree the help article below for backdoor Roth doesn't seem to be updated for the new screens. Form 8606 is also not finalized for filling not sure the sticking point but I don't think that affects these calcs.
First question just to confirm, do you have "earned" income like a W2? Otherwise your IRA contribution is not valid and will be flagged as an excess.
https://ttlc.intuit.com/turbotax-support/en-us/help-article/retirement-benefits/enter-backdoor-roth-...
