As I mentioned earlier this month, Old Company is opening enrollments tomorrow, the 15th.
I'd recommend contacting them ASAP, as enrollment might only be open a short time.
Last time it was fully opened was March 2019, and since then only very high limit/old cards were accepted (and sometimes not even then).
Right now there are no restrictions on the age or limit of cards as long as they are 6 months or older. See the previous post for what card issuers they take.
IMO, OldCompany is where everyone tradelining should have their cards. One of only 2 that I think puts in the right AU verification methods (time and money), and much better than the other option in terms of customer support and prompt payments (automated, so always on time). Their sales are very high as well, and trending up (due to a marketing company they hired to help find AUs), thus the request for more cards.
If you have cards enrolled elsewhere, or have been thinking about tradelineing, now is the time for sure. A lot of people PM me throughout the year and it sucks to be like "well, the good ones aren't enrolling, but you can roll the dice with some bad companies", so I'm excited they finally are able to enroll new cards again. :)
Feel free to PM me if you need a referral.