I would go with Black Silicon Sealant. Open the Sunroof; smear the Silicone sealant on the sealing edges of what is left of the original Sun Roof Seal and close the Sunroof.
If any excess comes out press it down into the Seal and wipe off the Excess that gets on the Paint.
If there is gaps in the Silicon Sealant and the Sunroof Seal that Plastic Nozzle thing that comes with the Silicone Sealant and cut the end so that you get a tiny bead when you squeeze the Tube and fill in any gaps.
If you use the Sealant sparingly it should also look OK.

However, I think a better start would be to clean out the Sunroof Drains so that any Water that leaks in can get out.

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84 300D, 82 Volvo 244Gl Diesel