What kind of solution do you mean? The ISRG Root X1 certificate is accepted in major root certificate stores for more than 5 years now. Let's Encrypt has decided to switch over to this root certificate without a new cross-sign: they have to be on their own without "assistance" of cross-signed roots some day. Only for Android there was a possibility to use a cross-signed cert of the already used (and now expired) root certificate from IdenTrust. But that is a very specific exemption which was only possible for a specific, but large group of users (older Android). No such highly specific situation is possible for other users.
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