Luke died peacefully at home on August 2, with his family by his side ... his wife, Beckey, announced in a YouTube video.

Known for his popular YouTube channel, "I Will Not Be Defeated," Luke was diagnosed in August 2022 with Stage 4 Leiomyosarcoma ... a rare type of cancer the Mayo Clinic says begins in smooth muscle tissue and then spreads into normal body tissue.

Luke was told his cancer was terminal -- he lived for about 2 more years, undergoing multiple rounds of chemotherapy.

When he posted his last YouTube video on July 18, Luke revealed the cancer was getting worse ... "It's really been f***ing hard ... never felt anything out of it. I've been out of breath, sick, phlegm, you name it."

Luke's last video was ominously titled, "End of life. Feel like death is on me..." He died 15 days after it was posted.

He's survived by his wife and their two kids ... 5-year-old Taylor and 3-year-old Scarlett.

Luke was only 35.