The manual: "Through the new sealing system a change is a minor matter."
Let the grill go cold.
Open the dome fully; a helper keeps hold of it.
Lift the clamp tabs on the dome rim slightly. Do not bend them open.
Take the sealing tape out.
Leave the stainless plate on the base rim: it is not a gasket.
Fit the new tape in reverse order, pressing the tabs back gently.
Gasket care, and older felt gaskets
Care (2019 FAQ): do not let fat drip onto the gasket, and take care with the grill brush near it. A probe cable can run under the gasket.
No interval: Monolith gives none. Change it when it is worn, burnt or leaks.
Older grills (felt, 201055-C), from the 2019 FAQ and Monolith's 2020 video "Dichtung erneuern": scrape the old felt off with a hob scraper without hurting the glaze, take off the glue with fine sandpaper, then stick the new strip on piece by piece, starting at the back, with nothing overhanging inside.