let register() handle the teardown

main.js

@@ -4,32 +4,23 @@ module.exports = class RibbonClasp extends Plugin {
   async onload() {
     this.settings = Object.assign({ order: [] }, await this.loadData());
     this.enforcing = false;
+    this.alive = true;
+    this.register(() => { this.alive = false; });
     // icons can attach within milliseconds of each other on startup
     // (resetTimer, or it fires 200ms after the first one instead of the last)
     this.debouncedEnforce = debounce(() => this.enforceOrder(), 200, true);
+    // disconnecting the observer doesn't stop an already-scheduled call
+    this.register(() => this.debouncedEnforce.cancel());
 
     this.app.workspace.onLayoutReady(() => {
       // not tied to our lifecycle; still fires if we were disabled during boot
-      if (this.unloaded) return;
+      if (!this.alive) return;
       this.patchRibbon();
       this.enforceOrder();
       this.observeRibbon();
     });
   }
 
-  onunload() {
-    this.unloaded = true;
-    this.observer?.disconnect();
-    // disconnect doesn't stop an already-scheduled call
-    this.debouncedEnforce?.cancel();
-
-    const ribbon = this.getRibbon();
-    // don't restore over someone else's patch, just go inert instead
-    if (ribbon && ribbon.onChange === this.wrapper) {
-      ribbon.onChange = this.originalOnChange;
-    }
-  }
-
   getRibbon() {
     return this.app.workspace.leftRibbon ?? null;
   }
@@ -44,8 +35,9 @@ module.exports = class RibbonClasp extends Plugin {
     const containerEl = this.getRibbonContainerEl(ribbon);
     if (!containerEl) return;
 
-    this.observer = new MutationObserver(() => this.debouncedEnforce());
-    this.observer.observe(containerEl, { childList: true });
+    const observer = new MutationObserver(() => this.debouncedEnforce());
+    observer.observe(containerEl, { childList: true });
+    this.register(() => observer.disconnect());
   }
 
   // hook the ribbon's own onChange so drags and hide/show toggles update
@@ -57,13 +49,18 @@ module.exports = class RibbonClasp extends Plugin {
     const original = ribbon.onChange.bind(ribbon);
     this.originalOnChange = original;
 
-    this.wrapper = (save) => {
+    const wrapper = (save) => {
       original(save);
-      if (save && !this.enforcing && !this.unloaded) {
+      if (save && !this.enforcing && this.alive) {
         this.recordOrder(ribbon);
       }
     };
-    ribbon.onChange = this.wrapper;
+    ribbon.onChange = wrapper;
+
+    this.register(() => {
+      // don't restore over someone else's patch, just go inert instead
+      if (ribbon.onChange === wrapper) ribbon.onChange = original;
+    });
   }
 
   enforceOrder() {