Remove outer leaves from Brussels sprouts; set aside. Halve sprouts; set aside.
Cook bacon in a large skillet until browned around edges and fat is rendered, about 4 minutes. Remove from heat. Allow to cool slightly, and chop.
Add chopped bacon to a medium size bowl.
Remove bacon fat from pan.
Add breadcrumbs to pan and cook, stirring often in a teaspoon of bacon fat, until brown and crisp, about 5 minutes. Transfer breadcrumb mixture to the bowl with bacon. Toss in thyme and lemon zest; set aside.
In the same skillet, heat 2 tablespoons oil to medium-high. Add reserved halved Brussels sprouts. Season with salt. Cook, tossing occasionally, until deeply browned all over, 5–8 minutes.
Reduce heat to low, cover skillet, and cook until tender, about 5 minutes.
Uncover skillet, add reserved leaves and 1 tablespoon lemon juice. Toss to combine.
Cook, tossing occasionally, until leaves are bright green and just wilted, 4–5 minutes.
Add remaining 1 tablespoon lemon juice and season with salt.
Transfer Brussels sprouts to a serving dish, drizzle with additional oil. Garnish with breadcrumb mixture.