I'm not aware of any such plans. Both the ISRG and IdenTrust root certificate still are on the list of trusted roots.
Given that there are no public announcements and no posts on any of the mailing lists where Apple typically announces changes like that, I would say this is just FUD. Unfortunately, that web hosting company is not the first one to try something like this:
The only known incompatibility with Apple products that I'm aware of was with iTunes podcasts, where Apple's backend software was unable to fetch feeds from HTTPS servers using a Let's Encrypt certificate, presumably because they were using an older version of Java that didn't include the IdenTrust root. However, this was fixed a couple of months ago on Apple's end.