I am using bootstrap styling in some parts of my app (v5.0.0-beta1) and just upgraded fritz2 to v0.9.1. Now I get this error related to the fritz2 styling. Does not break anything, but you might have a look at it.

style.kt?2304:31 unable to insert rule in stylesheet: Failed to execute 'insertRule' on 'CSSStyleSheet': Failed to parse the rule ':-moz-ui-invalid{box-shadow:none;}'. DOMException: Failed to execute 'insertRule' on 'CSSStyleSheet': Failed to parse the rule ':-moz-ui-invalid{box-shadow:none;}'.
    at eval (webpack-internal:///./kotlin-dce-dev/fritz2-styling-jsLegacy.js:3697:33)
    at Array.eval (webpack-internal:///./kotlin-dce-dev/fritz2-styling-jsLegacy.js:3707:68)
    at eval (webpack-internal:///../../node_modules/stylis/dist/stylis.mjs:68:5957)
    at se (webpack-internal:///../../node_modules/stylis/dist/stylis.mjs:68:5651)
    at Styling.addDynamicCss_puj7f4$ (webpack-internal:///./kotlin-dce-dev/fritz2-styling-jsLegacy.js:3763:7)
    at Styling.resetCss_61zpoe$ (webpack-internal:///./kotlin-dce-dev/fritz2-styling-jsLegacy.js:3756:10)
    at resetCss (webpack-internal:///./kotlin-dce-dev/fritz2-styling-jsLegacy.js:3790:27)
    at new Theme$Companion (webpack-internal:///./kotlin-dce-dev/fritz2-styling-jsLegacy.js:11092:5)
    at Theme$Companion_getInstance (webpack-internal:///./kotlin-dce-dev/fritz2-styling-jsLegacy.js:11109:7)
    at SpacesContext.left_bcpvvc$ (webpack-internal:///./kotlin-dce-dev/fritz2-styling-jsLegacy.js:2926:16)
eval @ style.kt?2304:31

Thanks for reporting. We have already an issue on that https://github.com/jwstegemann/fritz2/issues/318