The excess contribution penalty for a SEP contribution is a 10% penalty reported on Form 5330, a form not supported by TurboTax.
However, SEP contributions are reported by the IRA custodian on Form 5498 as being in a particular year, not for a particular year, and it's the responsibility of the employer, not the custodian, to track the allocation of contributions to particular years. Since you made the contribution intended for 2018 on March 29, 2019 (obviously not in 2020 as you indicated in your question), you can treat the contribution as a contribution for 2019 instead of as a contribution for 2018 (since it's your responsibility to allocate the contribution to the particular tax year) and, if it's a excess contribution for 2019, you should be able to obtain an explicit return of that contribution to avoid the 10% SEP excess contribution penalty.
Regardless of what you do with regard to the excess SEP contribution, that doesn't change the fact that you obtained a regular, taxable distribution from this traditional IRA.
The only other possibility, and I don't know if this approach is viable, would be to treat the $20,000 distribution as having be coded incorrectly and that it represents contribution plus attributable gain or loss. If there was a gain, you would have to do a reverse calculation to determine how much of the distribution was a proportionate gain with respect to the remainder of the distribution. If there was a loss, you would have to split the distribution between a loss-adjusted amount and the remainder which would still be a regular distribution.
