There is a signal bridge [0], but it is a little hacky. I would imagine moxie won't condone an 'official' bridge to matrix, given his stance on federated chat. Also: any realistic (short-term) bridges will have to basically be a man-in-the-middle, breaking the end to end crypto. In the (very?) long term MLS [1] may allow for e2ee through a bridge, but that would probably mean that signal has to explicitly support it. Given the track-record of OWS I personally doubt that would happen, but I'm just a random guy from the internet, so what do I know. I do know that the matrix people are looking at MLS and are willing to implement it in matrix if it finalizes, though they'll currently focus on their own megolm implementation, which is very close to being perfect, from my perspective.

[0] https://github.com/matrix-hacks/matrix-puppet-signal [1] https://datatracker.ietf.org/wg/mls/about/