Display EPSG:25833 maps

Hi,

Hopefulle some of you have a sollution for this:
Software works great, but the area that we live is unfortunatly to “unmapped” for build in maps, therefor we need to have a custom basemap displayed.

We want to use: https://geodata.npolar.no/arcgis/rest/services/Basisdata/NP_Basiskart_Svalbard_WMTS_25833/MapServer/WMTS/1.0.0/WMTSCapabilities.xml
The map loads just fine into Mapsmarker using CRS EPSG:4326 (Plate Carree).

But since the external map runs in EPSG:25833 the coordinates are off.

Is there any sollution to this?