From seeing what HBO did with Max after removing HBO Go, I'm thinking that after Showtime’s linear channel rebrands to Paramount Plus with Showtime on January 8th on all providers, which includes cable/sat/etc., the website will most likely allow you to log in through your provider as Showtime Anytime did. It would make little sense to me for them to call the linear channel Paramount Plus with Showtime and not allow you to then log into their website using your provider credentials. So just be patient as they transition.
This is what is shown now on the Paramount Plus help website,
"Can I sign in with my TV provider to stream Paramount+?
You can’t stream Paramount+ using your TV provider credentials."
https://help.paramountplus.com/s/article/PD-Can-I-sign-in-with-my-TV-provider-to-stream-Paramount
However, after using Google, I found a deep link that shows this as (potential) proof of this change on Paramount Plus, but this might be from when they originally did this before deleting this option (but why keep it unless they're planning on changing it back once the transition occurs?).
"How do I sign into Paramount+ via a TV provider?
On the Paramount+ website:
So, check back by going to paramountplus.com on or after January 8th to see if you're then able to log in through your TV provider. (They might add this sooner, so you may want to check this daily from this point on.)
If this isn't the case, you'll have to choose: if you DVR Showtime to watch your programing, then keep your linear channel subscription through your provider. If you prefer VOD (video on demand), then cancel the provider subscription and sign up with Paramount Plus with Showtime. You can also just cancel Showtime if this is too aggravating for you, or contact your provider and demand that they give you the option of using the Paramount Plus with Showtime website, else threaten to cancel Showtime.
Notes:
1) The Paramount Plus website doesn’t have DVR capabilities on their live channels.
2) You don't have the additional Showtime channels through Paramount Plus’s website, just East and West live Feeds. So, no Showtime 2, etc. (I really hope that Paramount adds these additional Showtime channels to their website, including "The Movie Channel/XTRA" and "Flix".)
3) Not everything that is on the live channels of Showtime is on VOD due to streaming rights, such as certain movies and first-run episodes, as you have to wait until the next day to stream the show.
4) FrankDuVal To delete Showtime from Roku, select the channel, tap the "star" key on your remote, and scroll to "Remove App."
5) FrankDuVal You should be able to watch your cable TV provider (which includes Showtime through them) through your Roku by adding their channel to Roku (select "Streaming Store" from the Roku menu, select "search," and either type in your provider's name or go to the "Popular Channels" category on the right of the search box and scroll through there. If you can't find your cable TV provider on your Roku device, didn't they provide you with their own Cable/Streaming TV box? If you use your Roku because your provider doesn't offer you a way to watch their content -- including Showtime on your TV, or you don't want to pay to rent their box, then perhaps it's time for you to cut the cord and sign up with a streaming TV service like Hulu + Live TV, Youtube TV, DirecTV stream, or etc., which will allow you to watch live TV including linear Showtime on your TV through your Roku without having to cast anything from your smart device. Just make certain if you do this just to cancel the TV package because you'll still need your provider for internet service, and also make certain that you're not bundled because you could be paying more for your other services without the TV package (but it might end up costing you the same since the streaming services are usually cheaper than cable TV). Most of these services also include VOD content with their channels and DVR service.
I did see January 8 somewhere in something I read. I'll see if ROKU has a revised app then. Here's to hoping!
