If end user purchase date is unknown factory warranty starts from manufacure time. If you have purchased it from accepted seller in Europe and you have trusted invoice/receipt from this seller warranty starts end user purchase date normaly.
If out of warranty, reason or other, there is also available most spare parts from Siglent as listed in service manual. Mostly they are not expensive. (they are not like car spare parts what are priced so that if you make new car using official spare parts it is perhaps 20 or 100 times more expensive).
If warranty covered case take first contact seller (if you have purchased it from Europe) and next place in this case is contact Siglent if seller is just only "parcel shipper" and can not help.
Because it is L model (7" TFT) it is not out of active state. (older small 5.7" TFT models are out of production and obsolete)
BTW, there is also just now + models in this SDS1000 (example SDS1102CML+) series (I do not mean new X+). (bit improved - example higher resolution display)