It is worth you place Ubuntu boot option in first place in order to to boot Ubuntu by default. In grub menu you can choose Mint, Windows or get into your UEFI.
You can try disabling Dell SupportAssist Pre-Boot System Performance Checker in EUFI settings (consult your user manual) or/and google related topics.
Dell support partition is nvme0n1p4, and it looks like nvme0n1p5 is Dell recovery partition, so I wonder why your system is trying to use that disk/partition.
It impossible to get an answer w/o knowing that TOSHIBA history (if ii was the only disk that came with your computer, before installing SSD, cloned but keep some old partitions w/o formatting the whole disk,...), also the way you have installed/upgrade or move your Windows system and how you use it for backups (if it is/was used to store Window recovery images,...).
Maybe you "only" need to update your firmware (i.e.install the latest BIOS version) or reset your UEFI/BIOS settings and configure again.If you don't know how to do it you´ d better even not try.
