This year it's not limited to Marriott, although doesn't really make sense for the others.
https://promo.united.com/offers/p2mMust register. Transfer by September 30th. Bonus posts by end of January (ime, not much earlier).
Terms and conditions:
Registration:
To qualify for this offer, members must register for the promotion between September 1, 2022, and 11:59pm EST on September 30, 2022 ("Promotional Period").
Qualifying activity:
A member must earn award miles as a result of one or more points to miles conversion transactions from any combination of MileagePlus hotel partner programs that offer a points to miles transfer program that are conducted during the Promotional Period ("Qualifying Activity") in order to qualify for MileagePlus Hotel Points-to-Miles bonus miles ("Bonus Miles"). Qualifying Activity must be completed by 11:59pm EST on September 30, 2022.
Posting of promotional miles:
At the conclusion of the promotion, all miles earned by each member from Qualifying Activity will be multiplied by 30% to determine the eligible bonus up to a maximum of 25,000 bonus miles. Bonus miles will be credited into the member's account on or before January 31, 2023. The maximum bonus miles that can be earned by a member under this promotion is 25,000. MileagePlus will not be responsible for technical problems with partner miles postings, or failures or delays in miles postings by hotel partners, that would render any points to miles converted as ineligible under this promotion.
