Having been supported by @IslaEvans + @Phoebebaxter (apologies if I have tagged the wrong Phoebe Baxter!), it was suggested I post here to gain further traction for getting Cymraeg (Welsh) as a supported language within Survey123 (and hopfully the remainder of Esri apps and products). Currently there is no Esri-defined text for any navigational buttons or tooltips within Survey123 web app like there is for other supported languages.
As a GIS & Data officer for the third sector in Wales, this is a massive blockade from us continuing to use Esri products. This is a shame as there is great potential in using said products. I hope this development is on the very near horizon, especially as this year's Welsh Esri Conference is looming!